RR is correct - most "disco" is from distinct red and green diodes spaced too far apart, but notice I said most. I have noticed it even with white and blue diodes alone. Unfortunately, the individual red/green diodes are there for a reason - some aquarists prefer the bump in color rendition they give.

RR is also correct with regards to shadows, to a point - fixtures with pucks can result in greater shadowing, but this can be mitigated through various means (height, lens removed/ not used, multiple pucks/ fixtures, T5 supplementation, etc.)

I will disagree with RR on one point - IMO, the Razor is much more aesthetically pleasing...